c++ - Qt客户端服务器应用程序 “send image”出现问题

我正在尝试通过Mat从客户端向服务器发送图像(OpenCV QDataStream)。第一项是int，即缓冲区的大小。它可以处理10到15张图像，然后服务器读取第一个int随机数(通常为〜2 ^ 30)，这会导致应用崩溃。
这是客户端，处于一个循环中(图像来自摄像头，周期为500ms):

//1) encode to jpg
 cv::vector<uchar> buf;
 cv::imencode(".jpg", *mat, buf);

 //2) write to buffer
 QByteArray buffer;
 QDataStream out(&buffer, QIODevice::WriteOnly);
 out << int(0); // save place for an int which represents the buffer size

 for(cv::vector<uchar>::iterator it = buf.begin(); it != buf.end(); ++it)
 {
  out << *it; //write each byte
 }

 out.device()->seek(0); //write the buffer size
 out << buffer.size();
 qDebug() << "Sent " << buffer.size() << "bytes";

 qint64 bytesSent = socket->write(buffer);
 if(bytesSent < buffer.size())
 {
  if(bytesSent != -1)
  {
   qDebug() << "Transmit Error! Sent " << bytesSent << " out of " << buffer.size();
  }
  else
  {
   qDebug() << socket->errorString();
  }
 }

服务器端:

QDataStream in(socket);
 int msgSize = -1;

 //first read the size as an int
 if(socket->bytesAvailable())
 {
  in >> msgSize;
 }

 qDebug() << "Read image size: " << msgSize << "bytes";
 //wait until all bytes all available
 while(socket->bytesAvailable() < ( qint64 ) ( ( qint64 )msgSize - sizeof(int) ) )
 {
  if(!socket->waitForReadyRead())
  {
   qDebug() << "Disconnected: " << socket->errorString();
   socket->disconnectFromHost();
   break;
  }
 }
 qDebug() << "Bytes recieved: " << msgSize;


 QByteArray ba;
 quint8 byte;
 for(int i = 0; i < msgSize - 1; ++i)
 {
  in >> byte;
  ba.append(byte);
 }
        cv::Mat imgbuf = cv::Mat(FRAME_WIDTH, FRAME_HEIGHT, CV_8UC3, ba.data());
 cv::Mat matImg = cv::imdecode(imgbuf, CV_LOAD_IMAGE_COLOR);

两个套接字都是QTcpSocket。

输出示例:

The server side:

Read image size: 67551 bytes
Bytes recieved: 67551
Read image size: 56924 bytes
Bytes recieved: 56924
Read image size: 70027 bytes
Bytes recieved: 70027
Read image size: -2046830337 bytes
Bytes recieved: -2046830337
Read image size: -536866742 bytes
Bytes recieved: -536866742
Read image size: 1179207168 bytes

At this point it tries to read 1179207168 bytes.

The client side:
Sent 67551 bytes
Sent 56924 bytes
Sent 70027 bytes
Sent 70277 bytes
Sent 85633 bytes
Sent 65155 bytes
etc ...

只有前三个成功。

最佳答案

首先，我认为您不需要QDataStream来完成此任务。 QDataStream用于序列化/反序列化Qt类型，并且特定于您使用的Qt版本。由于您只想通过网络编写uchar，因此您可以直接在cv::vector中进行迭代，然后直接通过网络写入这些字节(实际上，您不需要中间的QByteArray，因为您已经拥有了byteLength您的原始 vector )。

但是，您可以使用QDataStream(因为您使用的是非常基本的类型，这些类型在QDataStream版本之间可能不会更改)，并且由于您是从这种方式开始的，因此我将相应地提供答案

这看起来更像(客户端):

// 1) encode to jpg
cv::vector<uchar> buf;
cv::imencode(".jpg", *mat, buf);

// 2) write to buffer, your 'protocol' assumes buffer length first, then the data.
// REMEMBER: QDataStream operates on -any- QIODevice, so no need for the extra buffer here
QDataStream out(socket, QIODevice::WriteOnly);
out << buf.size();

cv::vector<uchar>::const_iterator it;
cv::vector<uchar>::const_iterator itEnd = buf.end();
for (it = buf.begin(); it != itEnd; ++it)
    out << *it;

服务器端:

QDataStream in(socket, QIODevice::ReadOnly);
cv::vector<uchar> buf;
socket->waitForReadyRead();

qint64 bytesRead = 0;
qint64 size;
in >> size;

buf.reserve(size);
while (buf.size() < size) {
    if (!socket->bytesAvailable())
        socket->waitForReadyRead();

    qint8 byte;
    in >> byte;
    buf.push_back(byte);
}

cv::Mat imgbuf = cv::Mat(FRAME_WIDTH, FRAME_HEIGHT, CV_8UC3, buf);
cv::Mat matImg = cv::imdecode(imgbuf, CV_LOAD_IMAGE_COLOR);

注意:完全可以解决，它很可能无法编译，并且肯定有一种更有效的方法，但是我认为它为您提供了如何修复现有代码的基本思路